Merge pull request #11978 from ahocevar/snap-delta-optional

Add snapToPointer option

src/ol/interaction/Modify.js

@@ -128,6 +128,8 @@ const ModifyEventType = {
  * provided, a vector source must be provided with the `source` option.
  * @property {boolean} [wrapX=false] Wrap the world horizontally on the sketch
  * overlay.
+ * @property {boolean} [snapToPointer=!hitDetection] The vertex, point or segment being modified snaps to the
+ * pointer coordinate when clicked within the `pixelTolerance`.
  */
 
 /**
@@ -386,6 +388,14 @@ class Modify extends PointerInteraction {
      * @type {Array<number>}
      */
     this.delta_ = [0, 0];
+
+    /**
+     * @private
+     */
+    this.snapToPointer_ =
+      options.snapToPointer === undefined
+        ? !this.hitDetection_
+        : options.snapToPointer;
   }
 
   /**
@@ -1163,8 +1173,10 @@ class Modify extends PointerInteraction {
         const vertexSegments = {};
         vertexSegments[getUid(closestSegment)] = true;
 
-        this.delta_[0] = vertex[0] - pixelCoordinate[0];
-        this.delta_[1] = vertex[1] - pixelCoordinate[1];
+        if (!this.snapToPointer_) {
+          this.delta_[0] = vertex[0] - pixelCoordinate[0];
+          this.delta_[1] = vertex[1] - pixelCoordinate[1];
+        }
         if (
           node.geometry.getType() === GeometryType.CIRCLE &&
           node.index === CIRCLE_CIRCUMFERENCE_INDEX